| Computer # |
| 2012.
 | 145 | Velocity Selective Arterial Spin Labeling at 7T Emiel C.A. Roefs1, Lydiane Hirschler1, Natalia Petridou2, and Matthias J.P. van Osch1
1Radiology, C.J. Gorter MRI Center, Leiden Univeristy Medical Center, Leiden, Netherlands, 2Radiology, Center for Image Sciences, Univeristy Medical Center Utrecht, Utrecht, Netherlands Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: Velocity selective (VS)-ASL can be of great added benefit for fMRI at ultra-high field because of its specificity and ATT-insensitivity. Goal(s): Our goal was to show the feasibility of VS-ASL at 7T with minimal TR, which involves minimizing SAR and timing parameters within the sequence. Approach: VS-ASL was implemented using BIR4 labeling module and compared to the robust FAIR ASL. Image quality was measured based on quantified ASL-signal and tSNR-efficiency. Results: Good agreement between FAIR and VSSinv-ASL was found. VSSinv-ASL was used to create intrinsic BGS without additional SAR. A shortest TR of 4500ms was achieved which could potentially be shorted with pTx. Impact: We showed the feasibility of Velocity Selective (VS)-ASL at UHF and the application in fMRI. VS-ASL showed comparable but less homogeneous tSNR as FAIR. VS-ASL is of added benefit for fMRI at ultra-high field because of its specificity and ATT-insensitivity. |
| 2013.
 | 146 | Whole-Brain SNR-Efficient Pseudo-Continuous Arterial Spin Labeling at 7T Joseph G. Woods1, Yang Ji1, Hongwei Li1,2, Aaron T. Hess1, and Thomas W. Okell1
1Wellcome Centre for Integrated Neuroimaging, FMRIB, Nuffield Department of Clinical Neuroscience, University of Oxford, Oxford, United Kingdom, 2Institute of Science and Technology for Brain-inspired Intelligence, Fudan University, Shanghai, China Keywords: Arterial Spin Labelling, Perfusion Motivation: The high SAR burden of PCASL at 7T typically requires long TRs and short label durations, reducing SNR efficiency and perfusion measurement accuracy. Goal(s): Our goal was to maximize the SNR efficiency of PCASL at 7T. Approach: We optimized the PCASL B1+/gradient parameters and background suppression pulses to maximize SNR efficiency (i.e., balancing labeling efficiency and SAR), and utilized VERSE and dynamic B0 shimming to reduce SAR.
Results: Compared to optimizing the PCASL parameters for maximum labeling efficiency, our max-SNR efficiency optimized parameters increased SNR efficiency by 38% and reduced TRs by 41% in vivo.
Impact: The improved SNR efficiency of our optimized 7T PCASL parameters increases the advantages of ultra-high field perfusion measurements, enabling robust and high-SNR perfusion measurement in clinically viable scan times.
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| 2014.
 | 147 | Machine Learning Based Approach for Partial Volume Corrected Cerebral Blood Flow and Arterial Transit Time Mapping Youngkyoo Jung1, Donghoon Kim2, Megan E Lipford3, Hongjian He4, Vladimir Ivanovic5, Samuel N Lockhart3, Christopher T Whitlow3, and Suzanne Craft3
1Radiology, University of California, Davis, Sacramento, CA, United States, 2Stanford University, Palo Alto, CA, United States, 3Wake Forest School of Medicine, Winston-Salem, NC, United States, 4Zhejiang University, Hangzhou, China, 5Medical College of Wisconsin, Milwaukee, WI, United States Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: To reduce a scan time of multi-PLD PCASL imaging using a convolutional neural network (CNN) for robust estimation of partial volume (PV)-corrected ATT and CBF maps. Goal(s): To develop a CNN to predict PV-corrected ATT and CBF from fewer PLDs, ensuring minimal accuracy loss. Approach: Trained and validated a CNN on multi-PLD ASL data from 48 subjects, comparing its performance with a standard method. Results: The CNN achieved low mean average errors, suggesting reduced PLD count does not significantly affect ATT and CBF estimation accuracy. Impact: The study’s CNN reduces MRI scan times while accurately estimating
brain hemodynamic parameters, such as cerebral blood flow and arterial transit time, enhancing patient comfort and diagnostic efficiency,
potentially transforming cerebrovascular disease monitoring and
advancing AI integration in medical imaging. |
| 2015.
 | 148 | Improving pCASL CBF mapping in neonates and adults with enhanced background suppression and complex subtraction Zhiyi Hu1, Dengrong Jiang2, Jennifer Shepard3, Yuto Uchida2, Kenichi Oishi2, Peiying Liu2,4, Doris Lin2, Vivek Yedavalli2, Aylin Tekes2, W. Christopher Golden3, and Hanzhang Lu1,2,5
1Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 2Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 3Department of Pediatrics, Johns Hopkins University School of Medicine, Baltimore, MD, United States, 4Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD, United States, 5F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, MD, United States Keywords: Arterial Spin Labelling, Perfusion Motivation: Standard arterial spin labeling (ASL) uses modest background-suppression to enhance SNR, which may not be optimal in reducing noise. Goal(s): Our goal was to further improve the SNR in ASL and reliably measure the cerebral blood flow (CBF) in low-perfusion scenarios such as neonates. Approach: We utilized an enhanced background suppression to minimize the signal from static background tissue. Complex subtraction of control/labeled signals was done to correct the magnetization sign-switching in between. Results: Enhanced background suppression combined with complex subtraction improved the reliability of CBF measurement in both neonates and adults, particularly benefiting the quality of neonatal CBF mapping. Impact: The improvement of SNR in ASL through enhanced background suppression coupling complex subtraction can facilitate the quality of cerebral blood flow measurement. The benefits are more pronounced in low-perfusion scenarios, such as bolstering the reliability of neonatal ASL. |
| 2016.
 | 149 | Impact of Bayesian-Inference vs Least-Squares Fitting on Multi-Delay Arterial Spin Labelling Parameter Estimation Aisling Fothergill1,2, Thomas Kirk3, David Higgins4, Aaron Oliver-Taylor5, Logan Zhang3, Martin Craig6, Michael A Chappell6, and Laura M Parkes1,2
1School of Health Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom, 2Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, Manchester, United Kingdom, 3Quantified Imaging, London, United Kingdom, 4Philips, Farnborough, United Kingdom, 5Gold Standard Phantoms Limited, London, United Kingdom, 6Sir Peter Mansfield Imaging Centre, School of Medicine, University of Nottingham, Nottingham, United Kingdom Keywords: Arterial Spin Labelling, Data Processing, Arterial Spin Labelling, Analysis, Bayesian, Kinetic Modelling Motivation: Multi-delay Arterial Spin Labelling has application across multiple patient groups, but accurate quantification remains difficult, particularly for prolonged transit times and noisy data. Goal(s): Compare least-squares and Bayesian-inference model fitting for perfusion estimate accuracy. Approach: Least-squares and Bayesian-inference, specifically BASIL, pipelines were run on simulated and in-vivo ASL data with different SNR with three choices of prior/initial value for arterial transit time (ATT). The resulting cerebral blood flow (CBF) and ATT maps were compared. Results: ATT quantification is impacted by ATT prior/initial value in Bayesian-inference fitting more than least-squares fitting. Least-squares fitting is more susceptible to CBF overestimation at lower SNR. Impact: MD-ASL analysis method can
impact ATT accuracy. Bayesian-inference fitting is better for lower SNR data when
CBF is the primary interest. Least-squares fitting is better for higher SNR
data, when prior/estimate is not well known, and for accurate ATT estimation. |
| 2017.
 | 150 | Multi-PLD ASL avoids up to 30% CBF underestimation in above half subjects without compromising test-retest reliability compared to single-PLD Zixuan Liu1, Qinyang Shou1, Kay Jann1, Danny JJ Wang1, and Xingfeng Shao1
1Laboratory of FMRI Technology (LOFT), Mark & Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States Keywords: Arterial Spin Labelling, Brain, Single-PLD, Multi-PLD Motivation: Long arterial transit time (ATT) may cause underestimation of CBF in single-delay arterial spin labeling (ASL) quantification. Goal(s): Our goal is to evaluate the accuracy and reliability between single- and multi-delay ASL acquisition. Approach: 28 subjects underwent test-retest scans ~1 week apart. Voxel-wise and regional CBF/ATT values were quantified to evaluate the test-retest reliability. ATT values obtained from 5-PLD data were used to estimate quantification errors for CBF estimated from single-delay (PLD=2s) ASL. Results: Overall, single-delay may cause an average of 4% to 30% of CBF underestimation in 56% regions. 5-delay is a solid solution to evaluate ATT and CBF. Impact: While single-delay ASL results in slightly higher test-retest reliability, the underestimation of CBF may compromise the quantification accuracy. Since ATT variation is more common in elderly and patients, multi-delay ASL with model-fitting analysis is expected to outperform single-delay ASL. |
| 2018.
 | 151 | Quantitative T2 of Long Post-Labeling-Delay (PLD) ASL Signal as a Reporter of Extravascular Microenvironment Zihan Wang1, Dinil Sasi Sankaralayam2, Sandeep Ganji3, Zhiyi Hu1, Wen Shi1, Dengrong Jiang2, and Hanzhang Lu1,2,4
1Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States, 2Radiology, Johns Hopkins University, Baltimore, MD, United States, 3Philips Healthcare, Rochester, MN, United States, 4F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, United States Keywords: Arterial Spin Labelling, Blood Motivation: Quantitative T2 values of ASL spins may then inform their local microenvironment. Goal(s): In this study, we aim to conduct a technical development to demonstrate the feasibility of measuring ASL T2 at long post-labeling-delay (PLD), at a time when the spins have fully exited the vasculature. Approach: A protocol comprised of Pseudo-Continuous Arterial Spin Labeling (PCASL) module followed by optimized background suppression pulses and 2D multiple-spin-echo (MSE) EPI readout was used to collect T2-weighted images at different post labeling delay (PLD). Results: We estimated T2 of ASL difference signals at long PLDs and also find age related changes in T2 values. Impact: Our result suggests that ASL spins may be used as a reporting probe to assessment the microvascular environment of the brain in health and diseases. |
| 2019.
 | 152 | Dynamic B0 field shimming for improving pseudo-continuous arterial spin labeling at 7 Tesla Yang Ji1, Hongwei Li1, Joseph G. Woods1, and Thomas W. Okell1
1University of Oxford, Oxford, United Kingdom Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: Increased B0 inhomogeneity along the length of brain-feeding arteries at 7 Tesla is one major issue for pseudo-continuous arterial spin labeling (PCASL), which reduces the labeling efficiency, leading to loss of perfusion signal. Goal(s): Our goal is to improve PCASL at 7 Tesla by specifically improving B0 field homogeneity of the vessels within the inversion region. Approach: We propose a vessel-specific dynamic B0 shimming method to optimize labeling efficiency without compromising the static shim over the imaging region. Results: Preliminary perfusion images indicate the superior performance of our proposed 3D dynamic shimming method over global or 2D-based correction methods. Impact: Our
proposed dynamic B0 shimming method demonstrates strong potential in
improving the robustness and effectiveness of PCASL, allowing the high
sensitivity and spatial resolution of 7T ASL to be fully utilized. |
| 2020.
 | 153 | Improving the Robustness of Pseudo-Continuous Arterial Spin Labeling in the Intraoperative MRI Setting. Carmen Sánchez-Albardíaz1, Marta Calvo-Imirizaldu1, Verónica Aramendía-Vidaurreta1, Marta Vidorreta2, Bartolomé Bejarano3, Lain H Gonzalez-Quarante3, Ana Aransay García3, Cristina Honorato4, Elena Cacho-Asenjo4, Antonio Martinez-Simon4, and María A Fernández-Seara1
1Radiology, Clínica Universidad de Navarra, Pamplona, Spain, 2Siemens Healthcare, Madrid, Spain, 3Neurosurgery, Clínica Universidad de Navarra, Pamplona, Spain, 4Anesthesia, Perioperative Medicine and Critical Care, Clínica Universidad de Navarra, Pamplona, Spain Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: Improvement of the intraoperative pseudo-continuous arterial spin labeling images for resection control in brain tumor surgery at 3T. Goal(s): Evaluate the effect of shortening RF pulse duration and gap on the labeling efficiency of PCASL and to test it in the intraoperative setting. Approach: A study in 10 healthy volunteers was done approximating the off-resonance effects at the labeling plane. 2 PCASL sequences were tested in 2 patients. Results: A PCASL sequence robust to off-resonance effects is obtained by shortening RF duration and gap. Impact: Shortening the RF duration and gap improves the PCASL
labeling efficiency at high B0 off-resonance values at the labeling
plane. |
| 2021.
 | 154 | Arterial Transit Time and Cerebral Blood Flow Estimation in Multi-delay Pseudo-continuous Arterial Spin Labeling Jiaxin Zheng1, Liangchen Shi1, Yong Zhang2, and Li Zhao1
1College of Biomedical Engineering & Instrument Science, Zhejiang University, Hangzhou, China, 2GE Healthcare, Shanghai, China Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: The inherent low SNR of ASL limits the accuracy of cerebral blood flow (CBF) and arterial transit time (ATT) quantification. Although a postlabeling delay weighted delay method has been proposed, its benefits are not clear and cannot be used in general delay protocols. Goal(s): To compare multi-delay protocols and estimators. Approach: A general weighted delay estimator was proposed. Its performance was evaluated using Monte Carlo simulations and in-vivo experiments, compared to the direct model fitting. Results: The multi-PLD/LD protocols provided a superior estimation compared to the other protocols. The L2-norm fitting and the GWD estimator may provide improved CBF and ATT estimation, respectively. Impact: The multi-PLD/LD protocols provided superior accuracy and precision which may provide a feasible option for quantifying the dynamic characteristics of perfusion. The L2-norm fitting and the general weighted delay method may provide improved CBF and ATT estimation, respectively. |
| 2022.
 | 155 | Reproducibility and sensitivity of BOLD-DSC Perfusion MRI within a single session and across multiple imaging sessions THUY THI LE1, GEUN HO IM1, CHAN HEE LEE1, and SEONG-GI KIM1
1Center for Neuroscience Imaging Research (CNIR), Institute for Basic Science (IBS), Suwon, 16419, Republic of Korea, Suwon, Korea, Republic of Keywords: Perfusion, Perfusion, DSC Motivation: Transient hypoxia-induced BOLD-DSC perfusion imaging approach can noninvasively map cerebral blood flow (CBF) and cerebral blood volume (CBV). However, the reproducibility of this technique has not been previously assessed. Goal(s): We aimed to determine the reproducibility of BOLD-DSC measurements within a single session and across multiple sessions. Approach: The reproducibility of trial-wise BOLD-DSC measurements within each session was assessed for each animal during week 1, while the reproducibility of weekly BOLD-DSC measurements was evaluated across all animals from week 1 to week 4. Results: We found that reproducibility and sensitivity of hypoxia-induced BOLD changes were consistently high in both single and multiple sessions. Impact: The
hypoxic challenge induces highly sensitive and reproducible BOLD responses
across trials within a single session and consistently across multiple sessions,
enabling the longitudinal and repetitive mapping of cerebral perfusion with easily
implementable whole-brain BOLD-DSC MRI in mice. |
| 2023.
 | 156 | Arterial deceleration time (ADT) mapping using velocity-selective arterial spin labeling Jia Guo1
1Bioengineering, University of California Riverside, Riverside, CA, United States Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: It is challenging to evaluate the health of vasculature at the arteriole/capillary level. Goal(s): To develop an approach to measuring a physiological parameter, arterial deceleration time (ADT), which may provide useful information at the arteriole/capillary level. Approach: Two sets of arterial transit time (ATT) measurement using VSASL with different Vcut in labeling but the same Vcut in imaging were carried out in one subject to measure ATT and ADT. Results: The preliminary data confirmed the ATT-insensitivity of VSASL and measured an ADT from 4cm/s to 2cm/s of less than 100 ms. Impact: This feasibility study measured a new physiological parameter: arterial
deceleration time – the time for the arterial blood to decelerate from V1 to V2
(V1>V2), which may have potential value in evaluating microvascular health
and clinical applications. |
| 2024.
 | 157 | Optimizing pseudo-continuous ASL at 7 Tesla using dynamic low order-shim update Yulin Chang1, Jason Stockmann2,3, Marta Vidorreta4, Natalie Wheeler2, Andreas Potthast5, Thomas Benner5, Manuel Taso1, John A Detre6,7, and Meher R Juttukonda2,3
1Siemens Medical Solutions USA Inc., Malvern, PA, United States, 2A.A. Martinos Center of Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, 3Harvard Medical School, Boston, MA, United States, 4Siemens S.A., Madrid, Spain, 5Siemens Healthcare GmbH, Erlangen, Germany, 6Department of Neurology, University of Pennsylvania, Philadelphia, PA, United States, 7Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States Keywords: Perfusion, Arterial spin labelling, shims Motivation: The labeling efficiency of pseudo-continuous ASL (pCASL) is reduced in the presence of large B0 off-resonance, which makes pCASL challenging at ultra-high fields due to susceptibility-induced off-resonance. Goal(s): We aim to significantly reduce the labeling efficiency dependence on B0 off-resonance of pCASL to achieve highest allowed labeling efficiency at a given labeling flip angle. Approach: 0th- (frequency) and 1st-order (x,y,z) shim components were used dynamically in the duration of labeling to mitigate B0 off-resonance without affecting imaging readout. Results: Improved labeling efficiency was achieved, which enabled higher-resolution perfusion imaging using pCASL. Selective labeling of blood was also demonstrated possible using our approach. Impact: Our approach provides a simple method to substantially remove the labeling-efficiency dependence on B0 off-resonance for pCASL at 7T. This enables high-quality ASL-based perfusion imaging at ultra-high fields for study of brain function, physiology, and pathology. |
| 2025.
 | 158 | Reduced B0/B1+ sensitivity in velocity-selective inversion ASL using adiabatic refocusing pulses Divya S Bolar1, Ryan Barnes1, Conan Chen1, Thomas Liu1, Fei Han2, Josef Pfeuffer2, and Eric Wong1
1Center for fMRI, University of California San Diego, La Jolla, CA, United States, 2Siemens Healthineers, Erlangen, Germany Keywords: Arterial Spin Labelling, Arterial spin labelling, velocity-selective ASL, CBF Motivation: Fourier transform velocity selective inversion (FT-VSI) ASL is sensitive to B0/B1+ inhomogeneities, which can lead to pronounced artifacts in CBF imaging. Goal(s): Reduce B0/B1+ sensitivity and improve performance of FT-VSI by utilizing adiabatic refocusing pulses in lieu of composite refocusing pulses. Approach: Adiabatic hyperbolic secant (sech) pulses with MLEV-8 phase modulation were integrated into the FT-VSI train, replacing the composite pulses. Simulations and phantom acquisitions were performed to evaluate B0/B1+sensitivity and subtraction fidelity. Human CBF data were acquired to compare image quality, tSNR, and artifacts. Results: Adiabatic refocusing markedly improved FT-VSI robustness to B0/B1+ inhomogeneities. CBF maps showed improved tSNR, image quality, and artifact reduction. Impact: A novel VSASL labeling train that uses adiabatic refocusing pulses for velocity selective inversion is introduced and found to dramatically enhance performance by improving accuracy, increasing tSNR, and reducing artifacts in human CBF imaging. |
| 2026.
 | 159 | Theoretical and experimental optimization of random vessel-encoded ASL to improve vascular territorial mapping and CBF quantification Yining He1, Jianing Tang1, Tianrui Zhao1, Maria Gamez2, and Lirong Yan1
1Biomedical Engineering, Northwestern University, Evanston, IL, United States, 2Radiology, Northwestern University, Chicago, IL, United States Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: Planning-free random vessel-encoded ASL (rVE-ASL) greatly simplifies the vessel-selective ASL scan settings and shows great potential for vascular territorial imaging in clinical applications. Goal(s): To theoretically and experimentally optimize rVE-ASL to establish an efficient and reliable rVE-ASL protocol
Approach: Simulation and in-vivo experiments were conducted to evaluate and optimize rVE-ASL in terms of labeling efficiency, total number of encoding steps, and reliability of vascular territorial and CBF measurements. Results: Reliable territorial mapping and CBF measurements from both ICA and VA can be achieved by optimized rVE-ASL. At least 20 encoding steps are needed to achieve reliable territorial mapping and CBF measurements in rVE-ASL. Impact: We have theoretically and experimentally optimized rVE-ASL, which can
provide reliable vascular territorial mapping and CBF quantification. The rVE-ASL technique holds a potential to be
a useful imaging tool for assessing vascular territorial alterations and
collaterals in various clinical applications. |
| 2027.
 | 160 | Optimizing velocity-selective inversion pulses for improved labeling efficiency and robustness Jia Guo1
1Bioengineering, University of California Riverside, Riverside, CA, United States Keywords: Arterial Spin Labelling, Arterial spin labelling Motivation: Current Fourier Transform-based velocity-selective inversion (VSI) pulses are sensitive to field inhomogeneities, leading to labeling errors or inefficiency. Goal(s): To improve the labeling robustness and efficiency of the VSI pulses for more robust and high-SNR perfusion measurement. Approach: A new design with 6-segment FT-VSI pulse was implemented and tested in healthy subjects using dual-module VSI labeling. Results: Compared with the existing VSI pulse, the new pulse significantly improved the labeling robustness against field inhomogeneities and the overall labeling efficiency, leading to >15% higher ASL signal (p<0.0002) and >20% higher temporal SNR (p<0.009). Impact: This new VSI pulse can effectively improve the labeling robustness
against field inhomogeneities, while increasing the labeling efficiency and
reducing the SAR. These features are especially beneficial with dm-VSASL implementation and in ultra-high field applications
for delay-insensitive ASL perfusion imaging. |